Gigabyte B550 Aorus Master has three working PCIe Gen4 M.2. SSD Slots

And that is very unusual actually. AMD is to release the B550 chipset soon, and motherboards normally would just get one M.2. slot at four PCIe gen 4.0 lanes. The chipset otherwise is Gen 3.0. So Gigabyte is being clever as frack and came up with a solution to bypass that limitation. 

Next to the single x4 lanes for one M.2. SSD, the Gigabyte B550 Aorus Master will split up the x16 PCIe Gen 4.0 graphics slot into a single 8x connection, that frees 2x four lanes. So any graphics card would run 8 lanes of PCIe Gen 4.0 and then all of a sudden you can use three m.2. SSDs at Gen 4.0. The B550 AORUS MASTER is a beefy one, it gets a 16-phase power supply, VRM cooling module, Realtek 2.5GbE network and Intel Wi-Fi 6 wireless.

The motherboard has reinforced RAM slots and the top PCIe slot is reinforced as well. It has 8+4 pins for the CPU which might indicate that this motherboard is designed with overclocking in mind. A release is expected in June, we'll see but this is a clever trick as x8 Gen 4.0 is the same bandwidth as x16 gen 3.0, e.g. any graphics card will run plenty fast on that slot. 

PCIe Version	Line Code	Transfer Rate	x1 Bandwidth	x4	x8	x16
1.0	8b/10b	2.5 GT/s	250 MB/s	1 GB/s	2 GB/s	4 GB/s
2.0	8b/10b	5 GT/s	500 MB/s	2 GB/s	4 GB/s	8 GB/s
3.0	128b/130b	8 GT/s	984.6 MB/s	3.938 GB/s	7.877 GB/s	15.754 GB/s
4.0	128b/130b	16 GT/s	1.969 GB/s	7.877 GB/s	15.754 GB/s	31.508 GB/s